Cleft hand, syndactyly and hypoplastic thumb.

The clinical features of 58 patients with typical cleft hand were examined and compared with 86 patients with syndactyly between the long and ring fingers, 27 patients with syndactyly between the ring, little and other fingers, 53 patients with hypoplastic thumb and 100 patients with symbrachydactyly. The clinical findings of the typical cleft hand resembled those of syndactyly. There were two unusual cases of typical cleft hand associated with hypoplastic thumb, congenital heart anomalies and absence of the axial triradius. One of these also had cleft lip and palate. The critical embryonic period of the heart anomaly is early, while that of the cleft lip and palate is late. These findings suggest that an embryo with typical cleft hand and hypoplastic thumb results from impairments at two different times in the early embryonic period.